Learn in the textbookFundamentals and Types of Virtualization
DefinitionVirtualization (仮想化) is a technology that handles physical resources such as the CPU, memory, and disks in software, so they can be used in a configuration different from the real one.
ExplanationA typical use is server virtualization, which divides one physical computer so it can serve as several environments. When each divided environment is built as a virtual computer, each one is called a virtual machine, and the OS running inside it is the guest OS. The reverse, bundling several physical resources so they appear as one, is also virtualization.
AnalogyThink of dividing a large open floor with partitions and renting it out as many private rooms. There is only one building, but each tenant uses their room as their own.
Memory hookVirtual means "not the real thing, but working as if it were." The same word gives the virtual in virtual machine and virtual memory.